iOS开发 Block传值

根视图：

#import "RootViewController.h"
#import "ModalViewController.h"

@interface RootViewController() {
    ModalViewController *modal;
}

@end

@implementation RootViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    //1) 设置背景颜色
    self.view.backgroundColor = [UIColor cyanColor];

    //2) 设置一个Label
    //a) 创建一个Label
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(25, 100, 270, 30)];
    //b) 设置该label的tag
    label.tag = 1000;
    //c) 设置label的内容
    label.text = @"Block的传值";
    //d) 设置背景颜色
    label.backgroundColor = [UIColor orangeColor];
    //e) 设置字体颜色
    label.textColor = [UIColor whiteColor];
    //f) 设置居中方式
    label.textAlignment = NSTextAlignmentCenter;
    //g) 添加label
    [self.view addSubview:label];

    //3) 设置跳转的button
    //a) 创建button
    UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
    //b) 设置其frame
    button.frame = CGRectMake(0, 0, 200, 30);
    //c) 设置其在屏幕的中心
    button.center = self.view.center;
    //d) 设置背景颜色
    button.backgroundColor = [UIColor lightGrayColor];
    //e) 设置显示的内容
    [button setTitle:@"跳转" forState:UIControlStateNormal];
    //f) 设置相应事件
    [button addTarget:self
               action:@selector(buttonAction:)
     forControlEvents:UIControlEventTouchUpInside];
    //g) 添加到页面上
    [self.view addSubview:button];

     //4) 初始化modal
     modal = [[ModalViewController alloc]init];
}

#pragma mark - button的响应事件
-(void)buttonAction:(UIButton *)button{
    // 防止内存泄漏
    __weak RootViewController *root = self;
    // 用block传值
    modal.block = ^(NSString *text){
        UILabel *label = (UILabel *)[root.view viewWithTag:1000];
        label.text = text;
    };
    // 控制器的跳转
    [self presentViewController:modal animated:YES completion:nil];
}

跳转视图：

#import "ModalViewController.h"

@implementation ModalViewController

-(void)viewDidLoad{
    [super viewDidLoad];

    //1) 设置背景颜色
    self.view.backgroundColor = [UIColor orangeColor];


    //2) 设置一个TextField
    //a) 创建一个TextField
    UITextField *textField = [[UITextField alloc] initWithFrame:CGRectMake(25, 100, 270, 30)];
    //b) 设置tag
    textField.tag = 2000;
    //c) 设置显示的效果
    textField.borderStyle = UITextBorderStyleRoundedRect;
    //d) 显示提示语
    textField.placeholder = @"请输入一段文字...";
    //e) 添加到self.view上
    [self.view addSubview:textField];


    //3) 设置跳转你的button
    //a) 创建button
    UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
    //b) 设置其frame
    button.frame = CGRectMake(0, 0, 200, 30);
    //c) 设置其在屏幕的中心
    button.center = self.view.center;
    //d) 设置背景颜色
    button.backgroundColor = [UIColor lightGrayColor];
    //e) 设置显示的内容
    [button setTitle:@"返 回" forState:UIControlStateNormal];
    //f) 设置相应事件
    [button addTarget:self
               action:@selector(backAction:)
     forControlEvents:UIControlEventTouchUpInside];
    //g) 添加到页面上
    [self.view addSubview:button];
}

#pragma mark - 按钮的响应事件
-(void)backAction:(UIButton *)button{
    // 获取当前输入框
    UITextField *textFiled = (UITextField *)[self.view viewWithTag:2000];
    // 给block传值
    if (self.block != nil) {
        self.block(textFiled.text);
    }
    // 关闭视图
    [self dismissViewControllerAnimated:YES completion:nil];
}